This invention relates to a method and apparatus for measuring bio-electrical potential changes in female mammalia to determine ovulation and constitutes an improvement over applicant's prior U.S. Pat. No. 3,924,609 entitled DETECTOR DEVICE AND PROCESS FOR DETECTING OVULATION.
Numerous efforts have been made in the art to accurately determine the timing and fact of ovulation as an aide for achieving or avoiding fertilization of an ovum by the timed presence or absence of male spermatozoa. These prior efforts include, for example, measurement of cyclical body temperatures, cytological evaluation of exfoliated cells in vaginal mucosa, endometrial biopsy, biochemical, including hormone change, analysis, and it has even been suggested to measure vaginal potential changes over a total ovulation cycle. See Yale J. Biol. & Med. 21: 249-253 (1949). These prior efforts exhibit inadequate sensitivity to low D.C. potentials to serve the purpose of easy, dependable, and accurate measurement, sufficient to provide an adequate, reliable indication at a remote measurement point of the deep-seated fact and timing of ovulation occurrence.
From initial studies on infrahuman mammals, followed by direct studies on the human female, basic research dating back to the mid 30's established a correlation between the physiological phenomenon of menstruation and ovulation and bio-electric body potentials.
During the menstruation cycle of a human female the ovum grows or ripens into a primary follicle each month, increasing many fold in size with a corresponding increase in the number of cells surrounding each ovum in several distinct tissue layers, the follice cavity being filled with liquid or follicular fluid in which the ovum is eccentrically disposed. Chromosome changes occur in the ovum and the structure of the follicle changes until spontaneous discharge of the ovum and fluid contents into the uterus in anticipation of fertilization. The cellular process leading to these changes is active with the elaboration of ovulatory enzymes which also affects the collagen supporting network of the follicle and ovary. A consequence is that for some 5 or 6 days before ovulation, the rapid growth of the ovum proceeds to the acutual event of ovulation. The follicle bursts and sweeps the ovum and fluid into the fallopian tubes ultimately to the uterus. That rupture of the follicle tissue in the presence of the streaming follicular fluid produces a predictable small potential which can be calculated. See, Electronstatics of Biological Cell Membranes, pages 83-106, R.M. Friedenberg, 1967 by North Holland Pub. Amsterdam.
Each phase of the ovulatory cycle, beginning with the periodic ripening of the follicle and ovulation through a final expulsion of the ovum from the uterus, signals small measurable electrostatic potentials variably developed and steadily rising with the succeeding steps of the process and which achieve a sharp peak of D.C. potential output at about the time of ovulation, then reducing, providing a direct current potential whose measurement allows the identification of the phase and timed sequence of this physiological event. The potentials of the cycle will change from a normally minus to a plus potential as the event proceeds reachng a maximum during ovulation. The ovum proceeds through the fallopian tubes and then to the uterus where it remains for about 12 hours awaiting fertilization at decreased potential; and after explusion, the potential slowly returns to a normal, minus, i.e., opposite polarity value.
In one case study, Messers Burr, Musselman, Banton and Kelly demonstrated that a positive bio-electric increase in potential occurred during ovulation in a human female on the 21st day of the menstrual cycle, which was confirmed at laparotomy. Burr et. al., BIO-ELECTRIC CORRELATES OF HUMAN OVULATION, Yale J. Biol. and Med. 10: 155, 1937.
Numerous electronic detecting instruments have been proposed to determine the timing of ovulation. One such prior known device comprises a vaginal probe consisting of two similar dual metal electrodes physically supported on an enlongated electrical insulating body with one of the electrodes disposed adjacent one end of the body and the other electrode disposed a further position down the length of the support body. In operation, the probe is connected to an indicator device, such as a high impedance FET balanced differential amplifier which is used to drive a meter. The probe is inserted into the vagina of a subject, until the last most electrode makes contact with the vaginal opening. This unit measures the electrochemical transformations in vaginal fluid to detect ovulation.
Instruments of this general design have proven to be somewhat inconvenient for the test subject and do not provide a remote measurement capability as desired.
A significant theoretical advance was achieved by the conception of applicant's prior detector device disclosed in U.S. Pat. No. 3,924,609. For a complete discussion of applicant's prior invention, the reader's attention is directed to this patent disclosure. Briefly, however, with applicant's prior system, a subject to be tested would grasp an electrode in each hand. Bio-electrical changes in potential of the subject were designed to be detected in the millivolt range by detection circuitry including a high impedance two section RC filter network, a differential to single ended operational amplifier, and active amplification networks.
The foregoing combined circuitry exhibited the characteristics of extremely high input impedance and high common mode rejection combined with isolation and filtration to indicate and measure low D.C. ovulation potentials.
Although applicant's prior detecting apparatus reflects at least a theoretical advance in the art, it has been determined that direct physical contact between the subject and the hand held electrodes imparts body electron contamination to the ionic bipotential signals being measured. Further, applicant's prior invention relied upon very high input impedances, in the range of 10.sup.10 ohms or greater, in conjunction with passive filtering to reduce the effects of AC signals which may be present. With such high input impedances, however, difficulties exist with respect to signal contamination from ambient sources such as domestic power lines, radios, business machines etc. Moreover high input impedances exacerbate the problems inherent in accurately balancing the system.
The difficulties suggested in the preceding are not intended to be exhaustive, but rather are among many which may tend to reduce the effectiveness and user satisfaction of prior ovulation measuring devices. Other noteworthy problems may also exist; however, those presented above should be sufficient to demonstrate that methods and apparatus for accurately and reliably detecting the timing of ovulation in female mammalia will admit to worthwhile improvement.